1. Field of the Invention
The present invention relates to a valve connector to be used, for example, for controlling a fuel evaporating gas (vapor) in piping such as evaporation piping or vapor return piping in a fuel supply system of a motor vehicle.
2. Description of the Related Art
In order to prevent fuel vapor gas generated in a fuel tank of a motor vehicle from being discharged into an atmosphere, a vapor discharge prevention mechanism that causes the vapor to be adsorbed in a canister has been widely employed. In this type of vapor discharge prevention mechanism, evaporation piping connecting a fuel tank and the canister uses a one-way valve or a check valve to maintain an appropriate pressure in the fuel tank by controlling a flow of the vapor. And, in the vapor discharge prevention mechanism, around a mouth of an inlet pipe and the fuel tank is connected by means of vapor return piping, a part of the vapor in the fuel tank is introduced to the mouth of the inlet pipe via the vapor return piping, and it is prevented that an external air is caught up in the mouth of the inlet pipe at fuel supply from outside. Thereby generation of the vapor is restrained. There is provided the one-way valve or the check valve in a middle portion of the vapor return piping for controlling a flow of the vapor according to an internal pressure of the fuel tank.
In this type of the evaporation piping or the vapor return piping, a rubber hose is connected to each end of the one-way valve or the check valve. And, an end portion of one rubber hose is connected to, for example, a connecting pipe on a side of a roll-over valve or a differential pressure regulating valve disposed on the fuel tank. Also, an end portion of the other rubber hose is connected to a connecting pipe on a side of the canister or a connecting pipe on a side of the inlet pipe. However, as there is a tendency to restrict strictly transpiration of a fuel from a fuel supply system, a resin tube is also used instead of the rubber hose. When the resin tube is used, in many cases, the resin tube is connected to the connecting pipe by means of a connector or a quick connector. And, under the increasing demand for low fuel transpiration in recent years, minute fuel transpiration from a connecting region between the rubber hose or the resin tube and the one-way valve, etc. cannot be ignored. So, there is a need to reduce the number of connecting regions between structural elements to lower fuel transpiration.
Accordingly, it is proposed that the one-way valve or the check valve is equipped or added in a quick connector having an inserting portion for the connecting pipe. Thereby the parts count itself, i.e. the number of parts in the evaporation piping, the vapor return piping or the like, and the number of the connecting regions between the structural elements is reduced to achieve low fuel transpiration.
A known type of quick connector, in which a one-way valve or check valve is equipped or added, comprises, for example, a connector housing that has a tube connecting portion on one axial end thereof and a pipe inserting portion on the other axial end thereof, a valve seat surface that is defined in an inner surface of the connector housing near the tube connecting portion, a valve body that is disposed in the connector housing so as to move toward and away from the valve seat surface in an axial direction, and a compression spring that is mounted in the connector housing for biasing the valve body toward the valve seat surface. Such type of quick connector is disclosed, for example, in Patent Document 1. The valve body closes the fluid flow path by abutting an abutting surface defined on an outer peripheral portion of a closing portion with the valve seat surface. The fluid flow path is opened when the valve body is subject to a fluid pressure from the one axial end and moves in a direction away from the valve seat surface.
[Patent Document 1] JP-A, 2004-116733
Meanwhile, in this type of valve connector disclosed in Patent Document 1, in order to secure stable operation of the valve body, a plurality of guides are provided in circumferentially spaced apart relation from one another, so as to extend from the closing portion in the direction away from the valve seat surface. Each of the guides is configured so as to be slidable over an inner peripheral surface of the connector housing when the valve body operates. Each of the guides has a support recess extending in an axial direction, and the compression spring is mounted in the connector housing while one axial end portion of a compression spring is received in the support recess and the other axial end portion of the compression spring is supported by a spring bearing that is formed on a side of the connector housing.
However, in such structure for supporting the compression spring, when the valve body moves or slides toward the spring bearing while compressing the compression spring, if a shocking vibration happens to act on the valve body, and thereby the valve body slides back toward the valve seat surface for a moment, the one axial end portion of the compression spring, for example, a part of the one axial end portion of the compression spring may come out of the support recess, and may be then caught in the other axial end portion of the guide. In this state, as a spring force of the compression spring is exerted to the valve body at an angle with respect to the axis, operation of the valve body becomes unstable, and as a result, certain pressure-flow characteristics of the valve connector cannot be maintained.
Under the circumstances described above, it is an object of the present invention to provide a valve connector having a structure for supporting a compression spring in its normal state constantly.